The 'On The Floor' singer will reunite with Steven Tyler and Randy Jackson on the judging panel for the show's 11th season, confirms Fox.
Lopez and Aerosmith frontman Tyler joined Jackson on the judging panel last season following the departures of Simon Cowell, Kara DioGuardi and Ellen DeGeneres.
Tyler and Jackson's returns were confirmed by the network earlier this year.
American Idol's creator and executive producer Simon Fuller said: "Having both Jennifer and Steven return to Idol in 2012 alongside Randy is such a positive reflection on what was a wonderful and hugely successful season last year, and everyone is delighted."
Lopez's place on the show had been in doubt earlier this summer when she admitted she was "on the fence" about reprising her judging role for a second season.
However, a return seemed to have been confirmed when the show's executive producer Nigel Lythgoe told host Ryan Seacrest's radio show last week that she had signed a deal for a second season.
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Mike Darnell, Fox's president of alternative programming, said: "From the very first day of auditions, we knew we had something special in our new judges' panel, and we're so happy that America felt that way too.
"Together with Ryan, who is fantastic day in and day out, they built an incredible connection with both the contestants and our viewers, and I'm absolutely thrilled to welcome them all back to Idol for another season."
Executive producer Cecile Frot-Coutaz added: "Their chemistry and ability to select amazing talent made last season one of our most successful yet, and we look forward to going on another exciting ride."
County singer Scotty McCreery was crowned the winner of American Idol's 10th season in May, beating Lauren Alaina in the live finale.
Auditions for the 11th season of American Idol continue in Houston, TX on August 26. Full details are available on the show's official website.
American Idol's new season premieres Sunday, January 22 on Fox.
Watch last season's winner Scotty McCreery's debut video for 'I Love You This Big' below: